Shift device with synchronizer

ABSTRACT

A shift device has lever members arranged between a sleeve, a hub, and synchronizer rings to amplify and transmit pressing force of the sleeve to at least one of the synchronizer rings. The lever members include first lever members for a first one of the synchronizer rings, and second lever members for a second one of the synchronizer rings. The first lever members and the second lever members are alternately arranged at two sides of the hub with a phase shift in a rotational direction.

The entire contents of Japanese Patent Application No. 2012-235111 filed Oct. 24, 2012 are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a shift device with a synchronizer for a transmission in which pressing force applied to a shift sleeve can be amplified into larger pressing force acting on a synchronizer ring while gears of the transmission are shifted, thereby reducing operating force necessary for a driver or an actuator.

2. Description of the Related Art

A shift device with a synchronizer for a transmission of this kind is disclosed in Japanese unexamined patent application publication No. 09-89002. This conventional shift device is used to shift gears between fifth-speed and reverse speed. It has a hub, a shift sleeve, a synchronizer ring capable of being pressed toward a fifth-speed gear, and a plurality of lever members provided between the synchronizer ring and the hub. The lever members change an axial pressing force from the shift sleeve into an amplified axial pressing force that acts on the synchronizer ring when the sleeve is being moved toward the fifth-speed gear, and they transmit the axial pressing force from the sleeve moving toward the reverse gear (in a direction opposite to the fifth-speed gear) to the fifth-speed gear so that the synchronizer ring and the fifth-speed gear are synchronized. This enables the sleeve rotating due to inertia of a clutch disc to stop the rotation thereof, and then the sleeve is smoothly engaged with the reverse gear. Thus the shift device can be a simple device using the lever members at lower manufacturing costs to decrease gear engagement noise in a shift operation to the reverse-speed position.

In the shift operation to the reverse-speed position, the friction torque of the synchronizer ring presses the lever members to extend them outwardly in the radial direction to prevent the sleeve from further advancing before the synchronization between the fifth-speed gear and the sleeve is ended.

When the synchronization is ended, the blocking force of the synchronizer ring due to the friction torque vanishes. Accordingly, the slanted surfaces formed on the inner surface of the sleeve press the lever members inwardly in the radial direction, so that the sleeve moves toward and engages with the reverse gear.

Another shift device with a synchronizer for a transmission of this kind is disclosed in Japanese unexamined patent application publication No. 2002-174261.

This conventional shift device has a plurality of lever members that are arranged at an axial middle position of a hub. The lever members are formed to be smaller to improve a shift feeling by decreasing operating force to push the lever members to an inner side after synchronization is ended to move a shift sleeve toward a high-speed gear in a shift operation at a high rotation speed. The same lever members are used to obtain in the synchronization toward one of the speed gears and the other thereof.

These conventional shift devices with the synchronizer, however, encounter the following problems.

In the former conventional device, the lever members thereof are inserted into a recessed portion (a groove portion formed in a circumferential direction) of the hub, being formed in an appropriately semicircular arc-like shape in a front view. This causes the lever members to become larger in the circumferential direction thereof. The thickness thereof needs to be larger to ensure the necessary stiffness, and accordingly they become heavier to generate larger centrifugal force that acts on the lever members during a shift operation at a high rotational speed. The larger centrifugal force causes a driver's operating force for moving the shift sleeve to be larger when it presses the lever members toward the inner side after the synchronization is ended. Therefore, the former conventional device cannot avoid from the deterioration in a shift feeling.

On the other hand, the latter conventional device can avoid from the deterioration in the shift feeling at the high rotational speed by using the lever members that are small in size and lighter in weight. The top portions of the lever members are, however, easily disengaged from inner splines of the shift sleeve when the lever members sometimes happen to be inclined toward a speed gear arranged at the one side in a state where the sleeve is engaged with another speed gear arranged at the opposite side. To avoid this problem, the shift sleeve needs to be formed larger in an axial direction thereof.

It is, therefore, an object of the present invention is to provide a shift device with a synchronizer for a transmission which overcomes the foregoing drawbacks and in which can decrease the both of the length in a circumferential direction of lever members and the axial length of a shift sleeve, ensuring a good shift feeling.

SUMMARY OF THE INVENTION

According to the present invention there is provided a shift device with a synchronizer which includes a shaft, a hub, a shift sleeve, two speed gears, two synchronizer rings, and a plurality of lever members.

The hub has a boss portion, a flange portion, and an annular portion. The boss portion is fixed to the shaft, the flange portion extends from the boss portion outwardly in a radial direction, and the annular portion is provided on an outer end portion of the flange portion and has outer splines on an outer side of the annular portion. A plurality of cut-off portions are formed at two sides of the hub in an axial portion to extend from the annular portion to the flange portion.

The cut-off portions are provided with first guide surfaces on the two sides in a rotational direction.

The shift sleeve has inner splines on an inner circumference side. The inner splines are provided with slanted surfaces, being engaged with the outer splines of the hub in such a way that the shift sleeve is supported on the hub to be movable in the axial direction.

The speed gears are rotatably supported on the shaft, being arranged at the two sides in the axial direction of the hub, respectively. The speed gears have splines engageable with the inner splines of the shift sleeve and a cone surface each at a hub side of the speed gears.

The synchronizer rings are arranged between the hub and the speed gears, respectively, to have a friction surface, a plurality of projections, and a plurality of pressure-receiving surfaces. The friction surface is provided on an inner side of the synchronizer ring so as to be capable of being pressed selectively on one of the cone surfaces of the speed gears. The projections are capable of transmitting friction torque generated between the cone surface of the speed gear and the friction surface of the synchronizer ring. The pressure-receiving surfaces are capable of receiving axial pressing force generated due to an axial movement of the shift sleeve. The lever members are arranged at the two sides of the hub among the shift sleeve, the hub and the synchronizer rings.

The lever members have a top portion and arm portions at two sides of the top portion to provide a leverage operation. The top portions are engageable with the cut-off portions of the hub and contactable with the slanted surfaces of the sleeve to function as a point of effort of the leverage. The arm portions are contacted with the hub to function as a fulcrum of the leverage, further being contactable with the pressure-receiving surfaces of the synchronizer ring to function as a point of load of the leverage so as to transmit pressing force of the shift sleeve to the synchronizer ring in the leverage operation. The lever members include a plurality of first lever members used for pressing one of the synchronizer rings and a plurality of second lever members used for pressing the other of the synchronizers. The first lever members and the second lever members are alternately arranged at the two sides of the hub with a phase shift between the first lever members and the second lever members in a rotational direction.

Preferably, the hub is provided with a plurality of recessed portions corresponding to the cut-off portions on the both sides of the flange portion. The recessed portions are formed with second guide surfaces parallel to the first guide surfaces. The lever members have arm portions at the both sides of the top portion in the rotational direction, the arm portions being formed on the both sides thereof in the rotational direction with a second slide surface corresponding to the second guide surface.

Preferably, the lever members are formed on the arm portions between the top portion and the second slide surfaces with torque-receiving surfaces capable of receiving the friction torque from the projections of the synchronizer ring in the synchronization operation.

Preferably, the recessed portions are formed to extend from the flange portion to the boss portion.

Preferably, the recessed portion at one side of the hub and the recessed portion at the other side thereof are partially overlapped in the axial direction.

Preferably, the shift device further includes a spring that always pushes the lever members outwardly in the radial direction.

Preferably, the spring includes elastic portions each acting elastic force to the corresponding lever member outwardly in the radial direction between the lever members and the boss portion of the hub. The elastic portions corresponding to the plurality of lever members are connected with each other.

Preferably, the spring includes at least one of a first surface and a second surface. The first surface is inserted between the lever member and the hub, and the second surface is inserted between the lever member and the pressure receiving surface of the synchronizer ring.

Preferably, at least one of the synchronizer rings includes a first synchronizer ring at an outer side in the radial direction, a second synchronizer ring at an inner side in the radial direction, and an intermediate ring arranged between the first synchronizer ring and the second synchronizer ring. The intermediate ring rotates together with the speed gear, being provided with a first cone surface and a second cone surface. The first synchronizer ring is provided with the friction surface capable of being pressed on the first cone surface, and the plurality of projections and the pressure receiving surfaces on a hub side of the first synchronizer ring. The second synchronizer ring is provided with a friction surface capable of being pressed on the second cone surface and a plurality of projections engageable with radially inner sides of arm portions of the lever member at the hub side. The lever members includes the arm portion at both sides of the top portion in the rotational direction, the arm portions being formed on inner sides thereof in the radial direction with second torque receiving surfaces capable of receiving the friction torque from the projections of the second synchronizer ring.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects, features and advantages of the present invention will become apparent as the description proceeds when taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a cross-sectional side view showing a shift device with a synchronizer of a first embodiment according to the present invention, taken along a line A-A in FIG. 2;

FIG. 2 is a front view showing a hub with lever members, a spring and a synchronizer ring, which are used in the shift device of FIG. 1;

FIG. 3 is a front view showing the hub from which the lever members, the spring and the synchronizer ring are removed;

FIG. 4 is a cross-sectional side view of the hub, taken along a line B-B in FIG. 3;

FIG. 5 is an enlarged cross-sectional view showing a part of a shift sleeve used in the shift device;

FIG. 6 is a front view of the synchronizer ring;

FIG. 7 is a cross-sectional side view showing the synchronizer ring, taken along a line C-C in FIG. 6;

FIG. 8 is a front view of the lever member;

FIG. 9 is a cross-sectional side view showing the lever member;

FIG. 10 is a front view showing the spring;

FIG. 11 is a top view showing the spring;

FIG. 12 is a cross-sectional side view explaining an operation of the first embodiment;

FIG. 13 is a cross-sectional side view showing a main part of a shift device of a second embodiment according to the present invention;

FIG. 14 is a front view showing a lever member of the second embodiment with which a projection of a second synchronizer ring is engaged;

FIG. 15 is a front view showing a spring used in a shift device of a third embodiment according to the present invention;

FIG. 16 is a top view showing the spring of the third embodiment; and

FIG. 17 is a front view showing a hub with lever members, a spring and a synchronizer ring which are used in a shift device of a fourth embodiment according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Throughout the following detailed description, similar reference characters and numbers refer to similar elements in all figures of the drawings, and their descriptions are omitted for eliminating duplication.

Referring to FIG. 1, there is shown a shift device of a preferred first embodiment according to the present invention, which is adapted for a transmission of a motor vehicle. In the embodiment, the shift device is applied to selectively obtain first-speed and second speed in the transmission.

The shift device includes an output shaft 1, a hub 12, a first-speed drive gear 2, a second-speed gear 4, a shift sleeve 20, two synchronizer rings 22 and two lever members 24.

The output shaft 1 is connected with a pair of drive wheels through a final unit having differential gears. The output shaft 1 is provided with outer splines 1 a on an external surface of a central portion thereof. The outer splines 1 a are engaged with inner splines of the hub 12, and the hub 12 is restrained from moving in an axial direction by using a bush 3 and a boss portion of the first-speed gear 2.

The first-speed gear 2 is rotatably supported on the output shaft 1 through a bearing 16 a between the boss portion 12 a of the hub 12 and a flange portion 1 b of the output shaft 1. Similarly, the second-speed gear 2 is rotatably supported on the output shaft 1 through a bearing 16 b between the boss portion 12 a of the hub 12 and a flange portion 3 a of the bush 3 fixed to the output shaft 1. Therefore, the first-speed gear 2 and the second-speed gear 4 are allocated at the both sides of the hub 12, respectively.

The first-speed gear 2 and the second-speed gear 4 are always engaged with a not-shown first input gear and a not-shown second input gear, respectively. These input gears are integrally formed with a not-shown input shaft arranged parallel to the output shaft 1 to be inputted with output power of an engine.

The first-speed drive gear 2 is provided at its hub side with spline teeth 2 a and a cone surface 2 b. Similarly, the second-speed gear 4 is provided at its hub side with spline teeth 4 a and a cone surface 4 b.

The first-speed drive gear 2 and the second speed gear 4 correspond to speed gears of the present invention.

As shown in FIGS. 3-4, the hub 12 has the boss portion 12 a, a flange portion 12 b extending from the boss portion 12 a outwardly in the radial direction, and an annular portion 12 d formed on an outer circumferential end portion of the flange portion 12 d. Two cut-off portions 12 e and two recessed portions 12 f are formed at each sides of the hub 12 to extend from the annular portion 12 to the flange portion 12 b. The recessed portions 12 f are arranged at positions corresponding to those of the cut-off portions 12 e, respectively. The cut-off portions 12 e and the recessed portions 12 f have 90 degree phase shift (Namely, they are arranged at 90° intervals.) in the rotational direction between at the first speed gear side and at the second speed gear side. The cut-off portions 12 e at the same side are arranged at the positions opposite to each other in the radial direction. Similarly, the recessed portions 12 f at the same side are arranged at the positions opposite to each other in the radial direction.

As shown in FIG. 1, the recessed portion 12 f at a first-speed gear side and the recessed portion 12 f of a second-speed gear side are partially overlapped with each other in the axial direction.

In addition, the cut-off portions 12 e are provided on the both sides thereof in the circumferential direction with a first guide portion 12 e, and the recessed portions 12 f are provided on the both sides thereof in the circumferential direction with a second guide surface 12 h parallel to the first guide surface 12 g.

Further, the recessed portions 12 f have a bottom surface 12 i at an inner side in the radial direction. As shown in FIG. 3, groove portions 12 k with an edge portion 12 j are provided in the vicinity of the bottom surfaces, respectively. The edge portions 12 j and the lever members 24 function as a fulcrum of the leverage as described below.

The shift sleeve 20 is arranged on the outer side of the annular portion 12 d of the hub 12 in such a way that inner splines 20 a formed on the inner surface of the sleeve 20 are always engaged with the outer splines 12 c of the hub 12 so as to be movable relative to the hub 12 in the axial direction. That is, in a state where the shift operation to the first-speed position is ended, the sleeve 20 is moved toward the right side in FIG. 1 and its inner splines 20 a are engaged with the spline 2 a of the first-speed drive gear 2. Similarly, in the state where the shift operation to the first-speed position is ended, the sleeve 20 is moved toward the left side in FIG. 1 and its inner splines 20 a are engaged with the spline 4 a of the second-speed drive gear 4.

The inner splines 20 a are formed on the both end portions thereof with a chamfer 20 b. In addition, the inner splines 20 a are formed with a cut-off portion 20 e along the circumference thereof at positions corresponding to the cu-off portions 12 e of the hub 12, and the cut-off portions 20 e are formed on end portions thereof with a slanted surface 20 d.

The cut-off portions 20 c and the slanted surfaces 20 d are arranged with 90 degree phase shift in the rotational direction between at the first-speed gear side and at the second-speed gear side.

FIG. 5 shows how to form the cut-off portions 20 c and the slanted surfaces 20 d of shift sleeve 20.

First, a groove 20 e with the slanted surfaces 20 d is formed on the inner splines 20 a at the middle position thereof. Then portions of the inner splines 20 a indicated by cross-hatchings in FIG. 5 are cut off. The slanted surfaces 20 d on remaining portions function as the points of effort of the leverage, and they press the top portions 24 a of the lever members 24 in the axial direction during the synchronization operation.

The sleeve 20 is further formed with a circular groove 20 f on the outer circumference thereof to receive a not-shown shift fork that is operated by a hand of a driver or an actuator so that the shift sleeve 20 can be operated to move in a right and left direction in FIG. 1. FIG. 1 shows a state where the shift sleeve 20 is positioned at a neutral position. The shift sleeve 20 is moved toward the right side in FIG. 1 to establish the first speed, while it is moved toward the left side to establish the second speed.

As shown in FIG. 1, the synchronizer rings 22 are arranged between the first-speed drive gear 2 and the hub 12 and between the second-speed gear 4 and the hub 12, respectively. As they are arranged symmetrically with reference to the hub 12, Hereinafter the first-gear side will be mainly described.

As shown in FIGS. 1, 6 and 7, the synchronizer ring 22 is formed on the inner side thereof with a cone-shaped friction surface 22 a corresponding to the cone surface 2 b of the first-speed drive gear 2 and it is formed with pressure-receiving surfaces 22 b at the hub side and with two projections 22 c each at two positions corresponding to the recessed portions 12 f of the hub 12. The projections 22 c are formed with slanted surfaces 22 d on pressure-receiving surface sides thereof. The slanted surfaces 22 d press the lever members 24 outwardly in the radial direction during the synchronization operation.

The pressure-receiving surfaces 22 b function as the points of load of the leverage, and they are pressed in the axial direction by the lever members 24.

As shown in FIG. 1, the two lever members 24 are arranged among the synchronizer rings 22, the hub 12 and the sleeve 20.

Specifically, the lever member 24 at the first-speed gear side is arranged in the recessed portion 12 f at the first-speed gear to correspond to first lever members of the present invention. The lever member 24 at the second-speed gear side is arranged in the recessed portion 12 f at the second-speed gear to correspond to second lever members of the present invention.

As shown in FIGS. 8 and 9, the lever members 24 are formed with the top portion 24 a at a middle portion thereof, and the top portion 24 a is formed with first slide surfaces 24 b on the both side surfaces thereof corresponding to the first guide surfaces 12 g of the hub 12 in the front view of FIG. 8.

In addition, the top portion 24 a is provided with arm portions 24 c at the both sides thereof, and the arm portions 24 c have the shape corresponding to the recessed portion 12 f of the hub 12. The arm portions 24 c are provided with second slide surfaces 24 d on the both ends thereof, and the second slide surfaces 24 d have the shapes corresponding to the second guide surfaces 12 h of the hub 12.

Therefore, the lever members 24 are capable of moving and swinging in the radial and axial directions with reference to the hub 12, being guided by the first guide surfaces 12 g and the second guide surfaces 12 h of the hub 12.

In addition, two torque-receiving surfaces 24 e are formed on the outer sides of the arm portions 24 c between the top portion 24 a and the slide surfaces 24 d, respectively, and two spring receiving surfaces 24 f are formed at the inner sides of the arm portions 24 f, respectively.

FIG. 2 shows a neutral state of the shift device, where there are a clearance E in the rotational direction between the torque receiving surfaces 24 e and the slanted surfaces 22 d of the synchronizer ring 22, so that the synchronizer ring 22 can rotate with the clearance E relative to the hub 12.

The clearance E is set in such a way that it becomes smaller when the synchronization is ended and the lever members 24 move inwardly in the radial direction so that a range where the synchronizer ring 22 can rotate becomes almost none.

The torque-receiving surfaces 24 e are set to respectively have an angle G, shown in FIG. 8, relative to the first slide surfaces 24 b and the second slide surfaces 24 d in such a way that they contact with the slanted surfaces 22 d of the synchronizer ring 22 so that the lever members 24 are pressed outwardly in the radial direction during the synchronization operation.

The top portions 24 a are formed with a slightly-round edge 24 g, shown in FIG. 9, on the hub sides thereof to be capable of being pressed by the slanted surfaces 20 d of the sleeve 20. The edges 24 g may be formed to have a slanted surface instead of the round surface. The edges 24 g function as the points of efforts of the leverage.

The arm portions 24 c are formed with an edge 24 h, shown in FIG. 9, at the hub sides of the inner portions thereof. The vicinities of the edges 24 g and the bottom surfaces 12 i of the hub 12 function as the fulcrums of the leverage during the synchronization operation.

In addition, the lever members 24 are formed at the hub sides thereof with a press portion 24 i, which presses the synchronizer ring 22 in the axial direction during the synchronization operation. The press portions 24 i function as the points of load of the leverage.

A spring 28 is arranged between the two lever members 24 and the boss portion 12 a of the hub 12.

The spring 28 employs a thin plate made of spring steel, having elastic portions 28 a respectively corresponding to the two lever members 24. The elastic portions 28 a have a supporting portion 28 b at intermediate portions thereof to contact with the hub 12, and a press portion 28 c at an end portions thereof to contact with the spring receiving surface 24 f of the lever member 24. The elastic portions 28 a act their elastic force on the lever members 24 outwardly in the radial direction. The two supporting portions 28 b are connected by a connecting portion 28 d shaped like a letter C. Therefore, the two lever members 24 are pushed only by the one spring 28.

The operation of the shift device of the first embodiment will be described. In order to shift from the neutral position shown in FIG. 1 to the first speed in a state where the rotational speed difference exists between the output shaft 1 and the first speed gear 2, the sleeve 20 is moved toward the first speed gear 2. The slanted surfaces 20 d of the sleeve 20 contact with the edges 24 g of the lever members 24 g, and the sleeve 20 presses the lever members 24 in the axial direction.

As the lever members 24 are pressed outwardly in the radial direction by the elastic force of the spring 28, the top portions 24 a of the lever members 24 a are pressed by the slanted surfaces 20 d of the sleeve 20 and moved, being swung. Then the press portions 24 i press the pressure-receiving surfaces 22 b of the synchronizer ring 22 at the first-speed gear side in the axial direction. Consequently, the friction surface 22 a of the synchronizer ring 22 is pressed on the cone surface 2 b.

As there is the rotational speed difference between the output shaft 1 and the first speed gear 2, the friction generates between the friction surface 22 a and the cone surface 2 b to apply friction torque to the synchronizer ring 22. This rotates the synchronizer ring relative to the hub 12 and the lever members 24 in one of the rotational directions to decrease the clearance E. In other words, as the synchronizer ring 22 is allowed to rotate with the clearance E relative to the hub 12 and the lever members 24, it rotates until the projections 22 c contact with the torque-receiving surfaces 24 e of the lever members 24. The friction torque acts on the torque-receiving surfaces 24 e to press the lever members 24 outwardly in the radial direction.

When the sleeve 20 presses the top portions 24 a of the lever members 24 in the axial direction, the lever members 24 amplifies the pressing force due to the leverage to press the synchronizer ring 24 as shown in FIG. 12 where a part of the hub 12 is removed so as to be easily understood.

That is, in the lever members 24, the edges 24 g of the top portions 24 a function as the point of effort, the edges 12 j where the vicinities of the edges 24 h contact with the hub 12 function as the fulcrums, and the press portions 24 i function as the points of load. The leverage ratio is L2/L1, where the lengths of L1 and L2 are indicated in FIG. 12.

Incidentally, the vicinities of the edges 24 h correspond to a first portion of the present invention, and the press portions 24 i correspond to a second portion of the present invention.

At this time, the friction torque generated between the friction surface 22 a and the cone surface 2 b press the torque receiving surfaces 24 e of the lever members 24 outwardly in the radial direction. The angles of the friction surface 22 a and the cone surface 2 b, the inclined angles of the slanted surfaces 20 d and the angles G of the torque receiving surfaces 24 e are set in such a way that the pressing force to the outer side becomes larger than the force where the lever members 24 are pressed to the inner side by the slanted surfaces 20 d of the sleeve 20.

Setting the angles like above, the sleeve 20 is prevented from further moving, pressing the lever member 24 inwardly in the radial direction, as long as the friction torque exists between the friction surface 22 a and the cone surface 2 b.

Accordingly, the sleeve 20 maintains to press the synchronizer ring 22 due to the leverage of the lever members 24 as long as the rotational speed difference exists between the output shaft 1 and the first speed gear 2. That is, the synchronization operation is carried out due to the friction torque generated between the friction surface 22 a and the cone surface 2 b.

This synchronization operation decreases the rotational speed difference between the output shaft 1 and the first speed gear 2, and the friction torque between the friction surface 22 a and the cone surface 2 b vanishes when the rotational speed difference becomes zero.

When the friction torque vanishes, the slanted surfaces 20 d of the sleeve 20 becomes to be able to easily press the lever members 24 inwardly in the radial direction and move toward the first speed gear 2. At this time, the synchronization operation ends, the sleeve 20 moves toward the right side in FIG. 1, pressing the lever members 24 inwardly in the radial direction. Then, the inner splines 20 a of sleeve 20 engage with the splines 2 a of the first speed gear 2. This is the end of the shift operation to the first speed.

Incidentally, the shift operation to the second speed 4 is similar to that to the first speed gear 2, its movement in the axial direction being inverse relation to that in the shift operation to the first speed gear 2.

The shift device of the first embodiment can provide the following advantages.

The shift device can improve the synchronization ability because of the leverage operation of the lever members 24. The lever members 24 include the first lever members for moving toward the first speed gear 2 and the second lever members for moving toward the second speed gear 4, and the first and second lever members are alternately arranged in the rotational direction with a phase shift between the first lever members and the second lever members. Accordingly, when the sleeve 20 engages with the first speed gear 2 for example, there is no possibility that the lever members 24 are inclined towards the second speed gear 4. Therefore, there is no need to set the axial length of the sleeve 20 larger, which enables the shift device to be smaller.

In addition, the lever members 24 can be set small in size and lighter in weight, so that the centrifugal force acting on the lever members 24 during the shift operation becomes smaller. Therefore, the shift device of the first embodiment can improve the shift feeling.

Further, the recessed portions 12 f at the first speed gear side and the second speed gear side of the hub 12 are partially overlapped with each other in the axial direction. Therefore, the axial length of the hub 12 can be smaller in the axial direction, thereby the hub 12 becoming to be smaller and lighter.

As described above, the shift device of the first embodiment can improve the shift feeling, being constructed as a compact one.

Next, a shift device with a synchronizer of a second embodiment according to the present invention will be described with reference to the drawings of FIGS. 13 and 14.

The second embodiment is different from the second embodiment in that the former is constructed as a shift device with a multi-cone type synchronizer. Specifically, an intermediate ring 32 is disposed between a first synchronizer ring 22 at an outer side and a second synchronizer ring 30 at an inner side. The intermediate ring 32 is provided with a first cone surface 32 a at an outer side and a second cone surface 32 b to be contactable with an inner fiction surface of the first synchronizer ring 22 and an outer cone surface of the second synchronizer ring 30, respectably.

A plurality of projections 32 c are provided on the first-speed gear side portion of the immediate synchronizer ring 32 to project in the axial direction so as to be engaged in holes 2 c formed on the first speed gear 2. This enables the intermediate ring 32 to be movable relative to the first speed gear 2 in the axial direction, being rotatable together with the first speed gear 2.

The second synchronizer ring 30 is provided with a friction surface 30 a and two projections 30 b at the hub side thereof, and with an end surface 30 c at the first-speed gear side thereof. The end surface 30 c contacts with an end surface 2 d of a boss portion of the first speed gear 2. In addition, the projections 30 b are contactable with the inner sides of the lever members 24 with a play E in the rotational direction as shown in FIG. 14.

Slanted surfaces 30 d are formed on the both sides of the projections 30 b in the rotational direction, corresponding to second torque receiving surfaces 24 g of the lever members 24.

Specifically, the second torque receiving surfaces 24 g are set to have an angle J (the same degrees as that of the angle G and in a direction opposite to the angle G) relative to the first and second slide surfaces 24 b and 24 d similarly to the first torque receiving surfaces 24 e. A clearance H is formed between the second torque receiving surfaces 24 g and the corresponding slanted surface 30 d.

The friction torque acting on the second synchronizer ring 30 in the synchronization operation is transmitted from the projections 30 b to the second torque receiving surfaces 24 g to press the lever members 24 outwardly in the radial direction.

Incidentally, the end surface 2 d of the first speed gear 2 and the end surface 30 c at the first-speed gear side of the second synchronizer ring 2 are formed as a flat surface in the embodiment, while they may be formed as a cone surface, the first speed gear 2 being formed with a cone surface 2 b and the second synchronizer ring 30 being formed with a third friction surface 30 d at the first-speed gear side. This structure is called as a triple cone type.

The other construction is similar to that of the first embodiment.

The operation of the shift device of the second embodiment will be described.

The operation of the second embodiment is basically similar to that of the first embodiment. The shift device of the second embodiment has the intermediate ring 32 between the first synchronizer ring 22 and the second synchronizer ring 30, and accordingly the operations are different after the lever members 24 press the first synchronizer ring 22.

That is, when the lever members 24 press the first synchronizer ring 22, this pressing force presses the friction surface 22 a against the first friction surface 32 a of the intermediate ring 32, and then it presses the second cone surface 32 b against the friction surface 30 a of the second synchronizer ring 30. Further, the end surface 30 c of the second synchronizer ring 30 press the end surface 2 d of the first speed gear 2.

Consequently, the friction torque can generate between the friction surface 22 a and the first cone surface 32 and between the second cone surface 32 b and the friction surface 32, thereby providing the synchronizer capacity higher than that of the first embodiment. The other operation is similar to that of the first embodiment, and it is omitted.

Incidentally, the number of the cone friction surfaces that generate the friction torque becomes three when the cone surface 2 b of the first speed gear 2 is formed with the third friction surface 30 d at the first-speed gear side.

The shift device of the second embodiment can provide the following advantage in addition to those of the first embodiment.

In the second embodiment, the force pressing the synchronizer ring 22 against a speed-change gear (the first speed gear 2 for example) becomes larger due to the leverage operation of the lever members 24 and the friction torque generates at two areas. Therefore, the synchronization capacity becomes higher.

Next, a shift device with a synchronizer of a third embodiment according to the present invention will be described with reference to the drawings of FIGS. 15 and 16.

The third embodiment is different from the first embodiment in a configuration of the spring 28 and also in that two springs 28 are provided for the lever members 24, respectively.

The springs 28 have an elastic portion 28 a similarly to that of the first embodiment. The elastic portion 28 a is provided at a central position thereof with a supporting portion 28 b contacting with the buss portion 12 a of the hub 12 and press portions 28 c at the both ends of the spring 28 contact with the spring receiving surfaces 24 f of the lever member so that the lever members 24 is pressed outwardly in the radial direction.

The hub-side supporting portion 28 b is bent in a direction at the right angle to form a first surface 28 e, the both ends of which are provided with a supporting surface 28 f. The supporting surfaces 28 f are inserted into the bottom portion 12 i of the hub 12 and the edges 24 h of the lever members 24. Accordingly, the supporting surface 28 f and the edges 24 h function as a fulcrum of the leverage.

On the other hand, a second surface 28 g is formed parallel to the first surface 28 e by being bent like a crank from the first surface 28 e. The second surface 28 g is inserted between the press portion 24 i of the lever member 24 and the pressure receiving surface 22 b of the synchronizer ring 22.

Incidentally, the axial length of the synchronizer ring 22 becomes shorter by the thickness between the supporting surface 28 f and the second surface 28 g.

The operation of the shift device of the third embodiment is as follows.

The operation of the third is basically similar to that of the first embodiment. The elastic portion 28 a of the spring 28 presses the lever members 24 outwardly in the radial direction.

The difference between the configurations of the springs 28 brings the difference operations therebetween.

Each first surface 28 f is inserted between the bottom portion 12 i of the hub 12 and the edge 24 h of the lever member 24, and accordingly the lever members 24 contact with the hub 12 through the supporting surfaces 28 f so as to act as the leverage.

In addition, each second surface 28 a is inserted between the press portion 24 i of the lever member 24 and the pressure receiving surface 22 b of the synchronizer ring 22, and accordingly the lever members 24 press the synchronizer ring 22 through the second surfaces 28 g in the leverage operation. The other operation of the third embodiment is similar to that of the first embodiment.

The shift device of the third embodiment can provide the following advantage in addition to those of the first embodiment.

The edges 24 b of the lever members 24 contact with the hub 12 through the supporting surfaces 28 f of the spring 28 when the lever members 24 press the synchronizer ring 22 in the leverage operation. Therefore, the hub 12 can easily ensure the durability to withstand wear without a hardening treatment.

In addition, similarly, the second surface 28 g of the spring 28 is inserted between the press portion 24 i of the lever member 24 and the pressure receiving surface 22 b of the synchronizer ring 22. Therefore, the synchronizer ring 22 can easily ensure the durability to withstand wear in a case where the synchronizer ring 22 is made of copper alloy, which is relatively soft.

Thus, in the third embodiment, the manufacturing costs of the hub 12 and the synchronizer ring 22 can be suppressed, the durability thereof being ensured.

Next, a shift device with a synchronizer of a fourth embodiment according to the present invention will be described with reference to the drawing of FIG. 17.

The fourth embodiment is different from the first embodiment in only the guide surfaces 12 g and the slide surfaces 2 b support the swing motion of the lever members 24 between the hub 12 and the lever members 24.

That is, the hub 12 has no second guide surface 12 h of the first embodiment, and the lever members 24 have neither arm portion 24 c nor second slide surface 24 d.

In addition, the recessed portions 12 f of the hub 12 are formed to extend in the boss portion 12 a thereof.

The lever members 24 are formed with a hole portion 24 j to engage with the projections 22 c of the synchronizer ring 22. A clearance E is formed in the rotational direction between the torque receiving surface 24 e and the projection 22 c of the synchronizer ring 22, so that the synchronizer ring 22 can be rotated with the clearance E relative to the hub 12.

Further, a spring 28 having a shape slightly different from that of the first embodiment is arranged between the lever members 24 and the boss portion of the hub 12.

The other construction of the fourth embodiment is similar to that of the first embodiment.

The operation of the shift device of the fourth embodiment is similar to that of the first embodiment.

The shift device of the fourth embodiment can provide the following advantage in addition to those of the first embodiment.

The recessed portions 12 f of the hub 12 is formed to extend in the boss portion 12 a thereof, so that shapes of the lever members 24 can be simpler, thereby the manufacturing cost being decreased.

While there have been particularly shown and described with reference to preferred embodiments thereof, it will be understood that various modifications may be made therein, and it is intended to cover in the appended claims and all such modifications as fall within the true spirit and scope of the invention.

The number of the lever members 24 is two in the embodiments, but it is not limited and it may be three or more. For example, when the three lever members 24 are used, they are preferably disposed to shift at intervals of 60° in the circumferential direction.

The speed gear is not limited to the first-speed gear or the second speed gear.

The friction surfaces may be formed with an oil groove or like a screw. They may be coasted on their surfaces with carbon material. 

What is claimed is:
 1. A shift device with a synchronizer comprising: a shaft; a hub having a boss portion fixed to the shaft, a flange portion extending from the boss portion outwardly in a radial direction, and an annular portion formed with outer splines on an outer side thereof, the annular portion and the flange portion being formed at two sides of the hub in an axial direction with a plurality of cut-off portions, and the cut-off portions being provided on the two sides in a rotational direction thereof with a first guide surface; a shift sleeve that is formed on a circumferential surface thereof with inner splines having slanted surfaces, the inner splines of the shift sleeve being engaged with the outer splines of the hub in such a way that the shift sleeve is movable in the axial direction; a pair of speed gears that are arranged at the two sides in the axial direction of the hub to be rotatably supported on the shaft, the speed gears being provided at each hub side thereof with a cone surface and outer splines engageable with the inner splines of the shift sleeve; a pair of synchronizer rings that are respectively arranged between the hub and the speed gears, the synchronizer rings being provided with a friction surface capable of being pressed selectively by one of the cone surfaces of the speed gears, and the synchronizer rings being provided at hub sides thereof with a plurality of projections projecting in the axial direction and a plurality of pressure receiving surfaces; and a plurality of lever members that are arranged at the two sides of the hub among the shift sleeve, the hub and the synchronizer rings, the lever members having a top portion engaged with a corresponding one of the cut-off portions of the hub and contactable with a corresponding one of the slanted surfaces of the shift sleeve to function as a point of effort of leverage, a first portion contactable with the hub functioning as a fulcrum of the leverage, a second portion connectable with the shift sleeve to function as a point of load of the leverage to transmit pressing force from the shift sleeve to a corresponding one of the pressure receiving surfaces in a leverage operation, and the lever members being capable of receiving friction torque from the projections of the synchronizer rings, wherein the lever members includes a plurality of first lever members configured to press a first one of the synchronizer rings, and a plurality of second lever members configured to press a second one of the synchronizer rings, and wherein the first lever members and the second lever members are alternately arranged at the two sides of the hub with a phase shift between the first lever members and the second lever members in the rotational direction.
 2. The shift device according to claim 1, wherein the hub is provided with a plurality of recessed portions corresponding to the cut-off portions on two sides of the flange portion, wherein the recessed portions are formed with second guide surfaces parallel to the first guide surfaces, and wherein the lever members have arm portions at two sides of the top portion in the rotational direction, the arm portions being formed on two sides thereof in the rotational direction with a second slide surface corresponding to the second guide surface.
 3. The shift device according to claim 2, wherein the lever members are formed on the arm portions between the top portion and the second slide surfaces with torque-receiving surfaces capable of receiving the friction torque from the projections of one of the synchronizer rings in a synchronization operation.
 4. The shift device according to claim 3, wherein the recessed portions are formed to extend from the flange portion to the boss portion.
 5. The shift device according to claim 4, wherein the recessed portion at a first one of the two sides of the hub and the recessed portion at a second one of the two sides of the hub are partially overlapped in the axial direction.
 6. The shift device according to claim 4, further comprising: a spring configured to always push the lever members outwardly in the radial direction.
 7. The shift device according to claim 6, wherein the spring includes elastic portions each configured to impart elastic force to a corresponding one of the lever members outwardly in the radial direction between the lever members and the boss portion of the hub, and wherein the elastic portions corresponding to the plurality of lever members are connected with each other.
 8. The shift device according to claim 6, wherein the spring includes at least one of a first surface and a second surface, and wherein the first surface is inserted between one of the lever members and the hub, and the second surface is inserted between the one of the lever members and a corresponding one of the pressure receiving surfaces of a corresponding one of the synchronizer rings.
 9. The shift device according to claim 2, wherein the recessed portions are formed to extend from the flange portion to the boss portion.
 10. The shift device according to claim 9, wherein the recessed portion at a first one of the two sides of the hub and the recessed portion at a second one of the two sides of the hub are partially overlapped in the axial direction.
 11. The shift device according to claim 3, wherein the recessed portion at a first one of the two sides of the hub and the recessed portion at a second one of the two sides of the hub are partially overlapped in the axial direction.
 12. The shift device according to claim 2, wherein the recessed portion at a first one of the two sides of the hub and the recessed portion at a second one of the two sides of the hub are partially overlapped in the axial direction.
 13. The shift device according to claim 12, further comprising: a spring configured to always push the lever members outwardly in the radial direction, wherein the spring includes elastic portions each configured to impart elastic force to a corresponding one of the lever members outwardly in the radial direction between the lever members and the boss portion of the hub, and wherein the elastic portions corresponding to the plurality of lever members are connected with each other.
 14. The shift device according to claim 12, further comprising: a spring configured to always push the lever members outwardly in the radial direction, wherein the spring includes at least one of a first surface and a second surface, and wherein the first surface is inserted between one of the lever members and the hub, and the second surface is inserted between the one of the lever members and a corresponding one of the pressure receiving surfaces of a corresponding one of the synchronizer rings.
 15. The shift device according to claim 1, wherein: the hub is provided with a plurality of recessed portions corresponding to the cut-off portions on two sides of the flange portion, and the recessed portion at a first one of the two sides of the hub and the recessed portion at a second one of the two sides of the hub are partially overlapped in the axial direction.
 16. The shift device according to claim 15, further comprising: a spring configured to always push the lever members outwardly in the radial direction, wherein the spring includes elastic portions each configured to impart elastic force to a corresponding one of the lever members outwardly in the radial direction between the lever members and the boss portion of the hub, and wherein the elastic portions corresponding to the plurality of lever members are connected with each other.
 17. The shift device according to claim 15, further comprising: a spring configured to always push the lever members outwardly in the radial direction, wherein the spring includes at least one of a first surface and a second surface, and wherein the first surface is inserted between one of the lever members and the hub, and the second surface is inserted between the one of the lever members and a corresponding one of the pressure receiving surfaces of a corresponding one of the synchronizer rings.
 18. The shift device according to claim 1, wherein at least one of the synchronizer rings comprises a first synchronizer ring at an outer side in the radial direction, a second synchronizer ring at an inner side in the radial direction, and an intermediate ring arranged between the first synchronizer ring and the second synchronizer ring, wherein the intermediate ring is configured to rotate together with a corresponding one of the speed gears, and is provided with a first cone surface and a second cone surface, wherein the first synchronizer ring is provided with the friction surface capable of being pressed on the first cone surface, and the plurality of projections and the pressure receiving surfaces on a hub side of the first synchronizer ring, wherein the second synchronizer ring is provided with the friction surface capable of being pressed on the second cone surface and a plurality of projections engageable with radially inner sides of the arm portions of the lever member at the hub side, and wherein the lever members include arm portions at two sides of the top portion in the rotational direction, the arm portions being formed on inner sides thereof in the radial direction with second torque receiving surfaces capable of receiving the friction torque from the projections of the second synchronizer ring.
 19. The shift device according to claim 1, further comprising: a spring configured to always push the lever members outwardly in the radial direction.
 20. The shift device according to claim 19, wherein the spring includes elastic portions each configured to impart elastic force to a corresponding one of the lever members outwardly in the radial direction between the lever members and the boss portion of the hub, and wherein the elastic portions corresponding to the plurality of lever members are connected with each other. 